Somebody mentioned in a thread a while back that some manufacturers mix their fuel by weight and others by volume so x% oil in one may not be the same as x% oil in another.

I mix by volume but have converted them to weights and use electronic scales to mix now so I don't need a separate mixing container, I just keep topping up the same old bottle adding new ingredients to old fuel and hitting the TARE button on the scales, it also keeps the molar proportions the same irrespective of fluid density changes due to temperature.

Anyway cut a long story short, it just so happens that in my brew of 20% oil (by volume), the percentage of oil by WEIGHT is 22.4%. Could be where YS got their 20%-23% range from?

Just for kicks same brew:
by volume = 15% nitro 20% oil 65% methanol
By weight = 19.4% nitro 22.3% oil and 58.3% methanol........